1. Field of the Invention
The present invention relates to a system on package (SOP), and more particularly to a SOP of a mobile radio frequency identification (RFID) interrogator to be built in a mobile terminal system of 900 MHz frequency band.
2. Description of the Related Art
Generally, a RFID interrogator (or a RFID reader) is implemented in portable or fixed type. The RFID interrogator supplies electric power to a RFID tag and interrogates a RFID code received from a RFID tag. A frequency band may be classified into 125 kHz, 134 kHz, 13.56 MHz, 433 MHz, 900 MHz, 2.45 GHz and 5.8 GHz according to the frequency band that a RFID interrogator uses.
Recently, researches about RFID techniques of 900 MHz frequency band that is similar with the frequency band for a mobile product such as a cellular phone are actively advanced.
Currently, most RFID interrogators of 900 MHz frequency band are fixed-type interrogators that are based on a patch antenna. Companies such as ALIEN or AWID manufacture independent-type interrogators that are based on an internal antenna. The interrogators for North America adopting the FCC Standards in which 902˜928 MHz frequency band and frequency hopping spread spectrum (FHSS) method are mainly used are manufactured owing to Wall-Mart.
Currently, the development of interrogators tends to be advanced toward satisfying the requirements of goods circulation fields including Wall-Mart. Most interrogators include a portable interrogator module and may be classified to a product type for industrial PDA, a PCMCIA type, and a module type according to the form of RFID interrogators. Also, the interrogators may be classified to a battery-internal type and a battery-separate type according to the form of electric power sources. There are differences of battery consumption between a 0.5-watt module and a 1-watt module. The interrogators operate continuously for 1˜2 hour(s) in technical level of the present time, and it is difficult to increase a duration time of a battery and efficiency of interrogators.
A module type interrogator, in which a module card is connected to a cellular phone typically has disadvantages such as inconvenience in use and portability because the interrogator is big in size.
As a cellular phone becomes small, light, and slim, a SOP of a RFID interrogator is needed in order to build a RFID interrogator in a cellular phone. In order to implement a small SOP of a RFID interrogator, there are relatively many technical difficulties compared with the module type interrogator that is big in size. For example, there are difficulties with respect to a mix of analog and digital signal processing, a design for reducing power consumption, a design for heat emission adaptable for a small size, and a design for improving signal integrity against increased signal interferences.